Silica coating apparatus for incandescent lamp bulbs



SILICA COATING APPARATUS FOR INCANDESCENT LAMP BULBS Sept", 1957 L. c.WERNER EI'AL 2 Sheets-Sheet 1 Filed De. 16, 1954 2 Mex E m W 5 2 N20? WW4 J mm 0% v 57/ 3 w% Y B Sept 17, 1957 L Q WERNER ErAL SILICA QOAT INGAPPARATUS FOR INCANDESCENT LAMP BULBS 2 Sheets-Sfieet 2 IN V EN TORfi'Filed Dec. 16, 1954 United States PatentO SILICA COATING APPARATUS FORINCANDESCENT LAMP BULBS Leo C. Werner, Cedar Grove, Stanley A. Lopenski,Pompton Plains, and Nicholas J. Rainone, Clifton, N. J., assignors toWestinghouse Electric Corporation, East Pittsburgh, Pa., a corporationof Pennsylvania Application December 16, 1954, Serial No. 475,656

5 Claims. (Cl. 118-51) The present invention relates to incandescentlamps and, more particularly, to improved silica coating apparatus forsuch lamps.

In the manufacture of high wattage incandescent lamps, for example, the100 watt gas fill type, various types of light diffusing coatings forthe lamp bulbs have been employed. In the past, frosting or etching ofthe incandescent lamp envelope has been most commonly used. Morerecently, a silica coating on the interior surface of the lamp bulb,deposited thereon preferably by electrostatic means, has been employed.

In the conventional apparatus for the electrostatic silica coating of anincandescent lamp bulb, the bulb is placed on a rotating chuck or headand is heated by a gas fire to render the glass envelope electricallyconducting. In addition, the hot ionized gas on the outside of the bulband the burner serve as a positive electrode. A silica powder nozzle andprobe which are reciprocable up and down within the lamp bulb seated onthe rotating chuck, serve as the negative electrode. The silica powderor smoke which is a mixture of high pressure air and finely suspendedsilica particles is blown from an aspirator at the bottom of acombination plowder pot and expansion chamber against a metal target inthe expansion chamber portion of the combination pot and expansionchamber. The larger particles or agglomerates fall back into the silicapowder below and the finely divided particles are blown into therotating bulb through the nozzle. The negatively charged silica powderparticles are repelled by the negatively charged probe and attracted tothe positively charged lamp envelope where they are firmly attached tothe bulb wall by the electrostatic field.

As the powder within the combination silica powder pot and expansionchamber is used, it is apparent that the silica powder volume willdecrease and the expansion chamber volume within the combination potwill increase. This means, assuming a constant silica delivery airpressure, that the density or fineness of the silica smoke thus producedwill vary, depending upon the amount of silica powder within thecombination pot. Again the silica powder tends to accumulate on the sidewalls of the combination pot, producing a crater effect andfeedingpowder to the discharge opening only from the crater-like center. 7

e A further defect of the conventional silica smoke gencrating apparatusis the inherent inability to clean out or clear the expansion chamber,between the coating cycles.

An additional defect of the conventional silica coating apparatus is theadherence of the silica smoke to the walls of the silica smoke deliverytubes, expansion chamber, aspir'ator, and silica powder pot.

A still further defect of the conventional silica coating apparatus isthe inability of the present lamp envelope heating burners to uniformlyheat the lamp bulb. The bulb is usually heated by a plurality ofindividual burners which are judicially juxtaposed about the bulbrotating on the chuck therebelow and are aimed at selected points on thelamp bulb surface.

The rubber or copper tubing which may connect the powder pot orreservoir and the expansion chamber or the aspirator at the bottom ofthe powder reservoir to the target within the expansion chamber, or thesmoke tube which connects the expansion chamber to the head are allsubject to the accumulation of silica smoke on the walls thereof. It isbelieved that the silica powder has a kinetic negative charge and therubber or copper tubing is positive. Thus the silica powder is attractedto the walls of the copper or rubber tubing and clean-out is renderedmore difficult.

Hence, it has been found advantageous according to the invention toprovide a separate expansion chamber suitably mounted on a cover of, andseparable from, the silica powder pot. The separate chamber will providea constant expansion chamber volume and more uniform generation of thesilica smoke will result. In addition, we have provided an invertedconically shaped powder spreader beneath a continuously rotated powderpaddle to prevent the crater-like accumulation of powder along the sidesof the silica powder pot and to insure a constant volume of silicapowder beneath the powder spreader and in contact with the powder potdischarge opening. Thus regardless of the amount of silica powder abovethe powder spreader a constant silica powder volume beneath the powderspreader and powder paddle insures a more uniform density of the silicasmoke.

Again it has been found advantageous according to the invention toprovide a solenoid operated bottom plate or plug for the expansionchamber mounted on the cover of the silica powder pot so that air may beblown back by means of a powder tube cleaner through the silica smoketube expansion chamber and the reciprocable bottom plug in its openposition to clean out any. agglomerates or heavy particles accumulatedwithin the expansion chamber after the last coating cycle. In ad'-dition, we have provided a porous bag affixed to the cover of the powderpot to act as a pressure relief valve or pressure dilfuser during theblow-back operation.

Further, it has been found advantageous according to the invention toprovide plastic tubing and a plastic coating for the expansion chamber"and powder pot. This tubing and coating may suitably be apolytetrafluoroethylene or the like. The plastic tubing and the plasticcoated expansion chamber and powder pot provide a smooth inner wallwhich prevents the silica powder from adhering thereto. In addition, theplastic has either a neutral or a negative charge which will either haveno attraction for, or repell, the negatively charged silica powder.

In addition, it has been found advantageous according to the inventionto provide a burner contoured to the outline of a vertical section ofthe rotating bulb. The burner may be provided with a plurality of burnertips or holes staggered in a zig-zag fashion to provide a fairly widesoft flame in contact with the entire surface of the lamp ibulb which isto be coated, thus insuring uniform coating thereof. 7

In its general aspect, the present invention has as its objective animproved electrostatic silica coating apparatus for incandescent lampbulbs.

A specific object of the present invention is an expansion chamberseparable from a silica powder reservoir to provide a constant expansionchamber volume and more uniform silica smoke.

An additional object is, an inverted cone-like powder spreader mountedbeneath a continuously rotatable powder paddle within the powderreservoir to prevent craterlike accumulation of powder along the sidewalls of the reservoir and to providea constant volume of silica =3powder beneath the powder spreader and in contact with a dischargeopening in the powder reservoir.

A still further object is an expansion chamber provided With amechanically operated bottom plate for intermittently connecting saidchamber to said powder reservoir and a powder tube cleaner for cleaningout accumulated agglomerates or heavy particles from the smoke expansionchamber.

A still further object of the invention is a powder reservoir providedwith a porous bag mounted on the cover thereof to act as a pressurerelief valve during the powder tube. cleaning operation.

A still further object of the invention is plastic tubing and a plasticcoating for the expansion chamber and powder reservoir to reduce theaccumulation of sillca smoke on the walls thereof.

Another object is a lamp bulb burner contoured to the outline of avertical section of said bulb to uniformly heat the entire surface ofthelamp which is to be coated.

Other objects of the invention will become apparent to those skilled inthe art to which it appertains as the description thereof proceeds bothby direct recitation and implication from the context.

Referring to the drawings in which like numerals of reference indicatesimilar parts throughout the several views:

Fig. l is a side elevational view partially in section of the improvedelectrostatic silica coating apparatus of the invention.

Fig. 2 is a plan elevational view of the silica powder reservoir andexpansion chamber and showing the chamber in section along the lineIL-II of Fig. l in the direction of the arrows.

Fig. 3 is. an enlarged vertical sectional view of the details of a lamphead and a powder tube cleaner of the invention.

Fig. 4 is a horizontal sectional view of the powder tube cleaneroperating mechanism along the line IV-IV of Fig. 3 in the direction ofthe arrows.

Fig. 5 is an enlarged vertical sectional view of a coating nozzle.

Referring now to the drawings in detail and particulady to Fig. l, thereference numeral designates an improved electrostatic coating apparatusof the invention. This apparatus 10 has a silica powder reservoir 11suitably mounted on a base plate of a frame 12 of an automatic silicacoating machine upstanding from the floor. The frame 12 may comprise astationary table 14 of generally elliptical shape mounted on a pluralityof integrated supporting members (not shown) and a base plate. The table14. carries a plurality of rotatable indexable heads 15.

The generally hollow hemispherical powder reservoir 11 may be providedwith a plate-like cover 16 (Figs. 1 and 2). An expansion chamber 18 ismounted by means of a suitable flange about a powder return opening 20in the cover 16. A bearing 21 (Figs. 1 and 2) may be Secured to thecover 16 for supporting a powder paddle shaft 22 journalled therein. Theshaft 22 extends through the cover 16 and carries a silica powder paddle24 on the lower end thereof. The shaft 22 is driven by suitable means,such as the motor 26 (Figs. 1 and 2). Adjacent the bearing 21, a hollowhub 26 is secured by its flange to the cover 16, as by bolts. The hub 26carries afiixed thereto a porous bag 28 which functions as a pressurerelease valve during an expansion chamber clean-out operationhereinafter to be described.

An inverted cone-like powder spreader 30 (Fig. 1) is mounted on thebottom portions of the powder reservoir 11, close to, but withsuflicient clearance from, the silica powder paddle 24. Silica powder 32is disposed about the powder paddle 24 within the powder reservoir 11,over the powder spreader 30 and adjacent to a discharge opening 36provided in the bottom portion of the powder reservoir 11. A retainingplate 38 supports a pipe 40 extending from the discharge opening 36 toan aspirator 42.

' may be threadable therein. A

A line 44 (Fig. l) connects one side of the aspirator 42 to a highpressure supply (not shown). A line 46 extends from the other side ofthe aspirator 42 through a mounting block 48 on the side wall of theexpansion chamber 18 and into said chamber 18. The lines or tubes 44 and46 may, according to the invention, be plastic, suitablypolytetrafluoroethylene.

Expansion chamber A silica powder target 50 (Figs. 1 and 2) isadjustably mounted adjacent to the delivery end of the tube 46 by meansof a rod 52 extending through the block 48 and adjustably held therein,as by means of a screw. It will be understood that by adjusting thedistance between the pipe 46 and the target 50 and the angle ofincidence between the silica powder 32 and the target 50, the silicasmoke turbulence within the expansion chamber 18 (and hence the silicasmoke density) may be controlled.

The expansion chamber 18 (Figs. 1 and 2) has a tapered bottom plate orplug 54 which seats in the powder return opening 20 in the cover 16.This plug 54 is carried on the lower end of an operating rod 56 of asolenoid operated air cylinder 58 mounted on a cover 59 of the expansionchamber 18. It will be understood that during the bulb coating portionof the cycle, the plug 54 separates the expansion chamber 18 from thepowder reservoir 11. During the expansion chamber clean-out portion ofthe operating cycle, the plug 54 is opened, thus permitting the heavyaccumulated agglomerates to deposit back (through opening 20) into thesilica reservoir 11.

A smoke tube 60 (Figs. 1 and 2) extends through the cover 59 and isconnected by means of a flexible plastic tube 62, suitablypolytetrafluoroethylene, to a silica smoke injector nozzle assembly 70.

Smoke injector nozzle assembly The smoke injector nozzle assembly 70(Figs. 1 and 3) is afiixed to one of the upwardly extending side wallsof a generally U-shaped bridge 72. This bridge 72 (Fig. 1) has a pair ofdownwardly depending guide hubs 74, only one of which is shown in Fig.1, and which are reciprocable on vertical rods or guides 76. The bridge72 is reciprocated through conventional connecting linkage (not shown)by a coating stroke cam (also not shown).

As shown in Fig. 3 an outer insulated coating sleeve having its upperinsulated portion 82 of reduced diameter and of insulating material,such as a suitable plastic, has a reinforcing metallic lower portion 84to provide rigidity thereto. An exhaust line 86, afifixed to an aperturein the lower portion of the lower sleeve 84, extends to an exhaustmeans, such as a pump (not shown). A lower cap 87 is secured, as bymeans of screws, to the bottom portion of the lower sleeve 84. It willbe understood that the lower end of the upper insulated portion 82, ofthe outer sleeve 80, is joined to the upper end of the lower metallicsleeve 84 of the outer sleeve 80, to form the outer sleeve 80.

The lower cap 87 (Fig. 3) supports and is secured to, by means of ascrew 90 to an axial coating tube 92 which extends substantially thelength of the outer sleeve 80. As shown in Figures 1 or 3 the lowerportion of the coating tube 92 is connected to the flexible tube 62 ofthe smoke tube 60. The coating tube 92 may be providedbelow its junctionwith the line 62 with a trap 94 (Fig. 1)

for collecting any heavy agglomerates not disposable through the exhaustline 86.

The upper end of the coating tube 92 (Figs. 1 and 3) carries afiangedcoating nozzle (Figs. 3 and 5) which plurality of annularly arrangedcoating outlets 102, for Example 8, having an inside diameter of about.040 may extend from the interior of the coating tube 92 through thenozzle 100. A probe 104 (Figs. 3- and 5) projects axially from the uppersurface of the nozzle 100 to serve as a negative side of a highfrequency, high voltage circuit (not shown).

lamp bulb 112.

Head

Each of the heads 15 (Figs. 1 and 3) has a hollow body or sleeve 130(Fig. 3) flanged at its upper end and provided with a pulley 132 on itslower end. This sleeve 130 has its flanged upper portion resting on andis rotatable in a bushing 134 carried by an annular retaining ring 136.These retaining rings 136 (shown in Fig. 3) liave flanged mountingportions on each end. The mounting portion on the left, when viewed inFig. 3, may be suitably lower than the flanged portion on the right, soas to permit the pinning together of the overlapping flanged portions ofadjacent retaining rings 136. These rings 136 are secured together toform a chain indexable from station to station on the periphery of thetable 14 of the machine by a conventional indexing means (not shown).

Each of the rings 136 (Figs. 1 and 3) carries an outer guide rail roller(not shown) and an inner indexing roller (not shown) transverse to thejoined ends. The indexing roller engages, and is indexed by, an indexingspider (not shown) located over the curved portions of the ellipticalflanged table 14. The guide roller rides on a rail (not shown) to insureproper alignment of a head 15 at the work stations.

A hollow lava insulating bulb chuck 138 (Fig. 3) has a flanged lowerportion 140 secured, as by lava pins, to the flanged upper portion ofthe hollow body 130 of the head 15. As shown in Fig. 3 the upper portionof the chuck 138 is suitably contoured to receive the neck portion of anincandescent lamp bulb 112.

Air blast powder tube cleaner An air blast powder tube cleaner 148 ofthe invention (Figs. 1, 3 and 4) is mounted adjacent a head 15 for useduring the indexing of said head 15 from station to station to clean outthe nozzles 100 (Fig. 5) and the adjacent parts of the silica smokeinjector nozzle assemblies 70. Each of the cleaners 148 has an arm 150(Fig. 4) mounted above the table 14 on a shaft 152. This shaft 152 iscarried by a support plate 152 affixed to the table 14, and is springbiased by means of a return torsion spring 153 (Fig. 3). A free end 154of the arm 150 (Fig. 4) is generally annular in shape and is providedwith an air blast tube 156 (Fig. 3) extending radially inwardly from theperiphery of the free end 154 to an air blast cleaner hole 158,extending vertically from the tube 156 to the bottom surface of the end154. The air blast cleaner line 156 is connected to a suitable source ofhigh pressure air (not shown) which may be actuated by a solenoidcontrolled valve (not shown) at the desired time.

It will be understood that the arm 150 is pivotable on the shaft 152adjacent a pulley 132 of a head 15 and carries a cam 159 (Fig. 4) inengagement with the pulley 132. The pulley 132 at a coating stationmaintains the arm 150 (through its cam 159) in its out position shown inthe solid lines of Fig. 4. When a head 15 indexes, the indexing pulley132 of a head 15 disengages itself from the non-indexing cam 159 thuspermitting the spring biased arm 150 to swing over into axial alignmentwith a coating nozzle 100 which is now in its retracted lowermostposition as shown in dotted line of Fig. 3. Simultaneously with thearrival of the air cleaner delivery hole 158 above the nozzle 100 ashort blast of high pressure air is released therethrough to the nozzle100, the coating tube 92, the upper portion 82 of the outer sleeve 80 ofthe smoke injector nozzle assembly 70 to the line 62, the smoke tube 60,the expansion chamber 18 and the now open plug 54 thereof and into thesilica powder reservoir 11, thus removing the powder agglomerates fromthe above-mentioned parts and returning them to the powder reservoir 11.

Itwill be understood that the solenoid operated air cylinder 58 (Fig. 1)on the expansion chamber 18 has opened the plug 54in the bottom of theexpansion chamber 18 prior to the indexing of a head 15 from the coatingstation of the machine 110.

Burner A burner (Figs. 1 and 3) contoured to the outline of a verticalsection of the bulb 112 is secured by means of a bracket 182 to table 14of the frame 12 of the coating machine. This burner 180 may beprovidedwith holes arranged in arrowhead zig-zag fashion in three rowsto provide a wide enveloping soft flame for uniformly heating the bulb112 to the desired electrical conductivity.

Thus, it will be seen from the foregoing description that we haveprovided, according to the invention, an improved electrostatic coatingapparatus 10. The apparatus 10 of the machine has a separate expansionchamber 18 suitably mounted on, and separable from, a cover 16 of asilica powder reservoir 11. The separate expansion chamber 18 provides aconstant expansion chamber volume and more uniform silica smoke.

In addition, we have provided an inverted cone-like powder spreader 30beneath a continuously rotated powder paddle 34 to prevent thecrater-like accumulation of powder 32 along the side walls of the silicapowder reservoir 11. The powder spreader 30 insures a constant volume ofsilica powder 32 beneath the powder spreader 30 and in contact with thepowder discharge opening 36 in the botom of the silica powder reservoir11 to provide a constant volume of silica thereat.

Further, we have provided a bottom plug 54, for the expansion chamber18, which is reciprocable by a solenoid operated air cylinder 58 mountedon the cover 59 of the expansion chamber 18, to seal the expansionchamber 18 from the powder reservoir 11. The plug 54 may be moved to itsopen position by the cylinder 58 to permit the removal of heavyparticles of silica powder 32 from the smoke injector nozzle assembly70, smoke tube 60 and expansion chamber 18 after the completion of thecoating cycle by means of the air blast powder tube cleaner 148. Theporous bag 28 mounted on the cover 16 of the powder reservoir 11 acts asa pressure relief valve during the air blast cleaning operation.

We have provided the inner surfaces of the powder reservoir 11, opening36, pipe 40, aspirator 42, line 46, expansion chamber 18, plug 54, smoketube 60, connecting line 62 and air tube 92 with a coating of a plastic,such as polytetrafluoroethylene. In fact, the tubes 40, and 46, smoketube 60 and tube 62 may be polytetrafluoroethylene and will have noattraction for, and hence will repel, the negatively charged silicapowder 32. A suitable polytetrafluoroethylene is manufactured by E. I.du Pont de Nemours & Co. Inc. of Wilmington, Delaware under the tradename of Teflon. Further, we have provided a burner 180 contoured to theoutline of a vertical section of the rotating bulb 112 on the head 15.The burner 180 may be provided with a plurality of burner tips orsuitable holes staggered in zig-zag fashion to provide a wide soft flamefor contacting the entire surface of the rotating bulb 112 which is tobe coated.

Although a preferred embodiment of the invention has been disclosed, itwill be understood that modifications may be made within the spirit andscope of the invention.

We claim:

1. An improved silica coating apparatus for incandescent lamp bulbscomprising a frame, a silica powder reservoir on said frame, anexpansion chamber mounted on said reservoir, means on said expansionchamber for separating said expansion chamber from said reservoir, anaspirator near said reservoir for delivering silica smoke to saidexpansion chamber, a hollow rotatable head for securing a lamp bulb tobe coated thereon, andmeans for connecting said expansion chamber tosaid head.

2. An improved silica coating apparatus for incandescent lamp bulbscomprising a frame, a silica powder reservoir on said frame, anexpansion chamber mounted on said reservoir, means on said expansionchamber for separating said expansion chamber from said reservoir, anaspirator near said reservoir for delivering silica smoke to saidexpansion chamber, a hollow rotatable head for securing a lamp bulb tobe coated thereon, a smoke injector nozzle assembly on said framebeneath said head and reciprocable within said head, and means forconnecting said expansion chamber to said smoke injector assembly.

3. An improvedsilica coating apparatus for incandescent lamp bulbscomprising a frame, a silica powder reservoir on said frame, anexpansion'chamber mounted on said reservoir, means on said expansionchamber for separating said expansion chamber from said reservoir, anaspirator near said reservoir for delivering silica smoke to saidexpansion chamber, a hollow rotatable head for securing a lamp bulb tobe coated thereon, a smoke injector nozzle assembly on said framebeneath said head and reciprocable within said'head, means forconnecting said expansion chamber to said smoke injector assembly, andan air blast powder tube cleaner on said frame adjacent said head forcleaning out said smoke injector assembly and said expansion chamber.

4. An improved silica coating apparatus for incandescent lamp bulbscomprising a frame, a silica powder reservoir on said frame, anexpansion chamber mounted on said reservoir, means on said expansionchamber for separating said expansion chamber from said reservoir, anaspirator near said reservoir for delivering silica smoke to saidexpansion chamber, a hollow rotatable head for securing a lamp bulb tobe coated thereon, a smoke injector nozzle assembly on said framebeneath said head and reciprocable Within said head, means forpositively charging a bulb and negatively charging an associated smokeinjector nozzle assembly, means for connecting said expansion chamber tosaid smoke injector assembly, an air blastipowder tube cleaner on saidframe adjacent said head for cleaning out said smoke injector assemblyand said expansion chamber, and means on said frame positioned adjacentsaid bulb in the plane of the longitudinal axis of rotation foruniformly heating said bulb for improved electrical conductivity.

5. An improved silica coating apparatus for incandescent lamp bulbscomprising a frame, a silica powder reservoir on said frame, anexpansion chamber mounted on said reservoir, means on said expansionchamber for separating said expansion chamber from said reservoir, anaspirator near said reservoir for delivering silica smoke to saidexpansion chamber, a hollow rotatable head for securing a lamp bulb tobe coated thereon, a smoke injector nozzle assembly on said framebeneath said head and reciprocable within said head, means forpositively charging a bulb and negatively charging an associated smokeinjector nozzle assembly, polytetrafluoroethylene means for connectingsaid expansion chamber to said smoke injector assembly, an air blastpowder tube cleaner on said frame adjacent said head for cleaning outsaid smoke injector assembly and said expansion chamber, and means onsaid frame positioned adjacent said bulb in the plane of thelongitudinal axis of rotation for uniformly heating said bulb forimproved electrical conductivity.

References Cited in the file of this patent UNITED STATES PATENTSl,900,104 Hageman et al Mar. 7, 1933 2,046,360 Bohlke July 7, 19362,336,946 Marden et al. Dec. 14, 1943 2,426,016 Gustin et al Aug. 19,1947 2,438,561 Kearsley Mar. 30, 1948 2,593,920 Reynolds Apr. 22, 19522,679,822 Kuebler June I, 1954 2,706,963 Hug Apr. 26, 1955

1. AN IMPROVED SILICA COATING APPARATUS FOR INCANDESCENT LAMP BULBSCOMPRISING A FRAME, A SILICA POWDER RESERVOIR ON SAID FRAME, ANEXPANSION CHAMBER MOUNTED ON SAID RESERVOIR, MEANS ON SAID EXPANSIONCHAMBER FOR SEPARATING SAID EXPANSION CHAMBER FORM SAID RESERVOIR, ANASPIRATOR NEAR SAID RESERVOIR FOR DELIVERING SILICA SMOKE